Accident Prevention Insole

ABSTRACT

An accident prevention insole includes a base surface ( 2 ) and a top surface ( 3 ) opposite to the base surface ( 2 ). The accident prevention insole ( 1 ) consists of a multilayer fabric ( 4 ) which can be crossed-through from the base surface ( 2 ) to the top surface ( 3 ) and vice versa by needles with a diameter lower than 14 tenths of millimetres perpendicularly driven to the insole with a load of at least 90 N, for directly sewing the insole to an upper ( 101 ) of a footwear ( 100 ), preferably with a Strobel technique.

The present invention relates to an accident prevention insole.

By accident prevention insole is understood to mean, in the context of this invention, an insole having mechanical, chemical and physical features which prevent the perforation of the same from pointed objects which can cause serious damages to a user.

More particularly, by accident prevention insole it should be meant an insole which can not be crossed through by nails with a diameter of 4.5 mm, or with higher diameters, perpendicularly driven at a speed of about 10 mm per minute, against the same with a force arriving up to 1100 Newton. Such values substantially coincide with those required by the rules in force on the accidents prevention.

The accident prevention insoles of the known art essentially consist of a properly shaped metal foil.

Such foil is inserted in the insole of the footwears of individual protection such that to be interposed between the ground and the sole of a user wearing the footwear. More particularly, the accident prevention insoles of the known art are positioned in a small interstice obtained in the sole of the shoe, usually in a plastic material, for being subsequently hold in a working position through the introduction of filling material in the interstice of the sole.

In this way, also following to an accidental placing of the user's foot on a nail, or an object assimilable thereto, the nail penetrates the sole and is arrested by the insole in a metal material, preventing the nail from reaching the user's sole and therefore preserving the same by a serious damage.

The Applicant has found that the accident prevention insoles of the known art are ameliorable under different aspects.

Firstly, the accident prevention insoles of the known art offer to the user a protection degree which is not always satisfying.

In fact, it is possible that a pointed body, such as a nail, penetrates the shoe sole and reaches the foot of the user without meeting the sole resistance. Such occurrence, which inevitably causes a disabling wound to the user, is due to the fact that the metal insole is not able to arrest nails which laterally penetrate the sole with such an inclination, with respect to the plane defined by the insole, that it does not intercept the metal insole but, however, is capable to reach the foot of the user.

In fact, as the metal insole must be inserted in the shoe sole, it is necessary that the print, namely the plan projection of the metal insole, is always smaller than the sole print, so as to ensure that during the walk the insole does not exit the sole. In other words, there always exists a space between the back end of the shoe an the back end of the metal insole, between the front end of the shoe and the front end of the metal insole and between the side ends of the shoe and the side ends of the metal insole. When a nail drives through these spaces, it does non find any resistance and it reaches the user's foot.

Furthermore, as mentioned, it is required to insert the metal insole within a proper interstice and block it therein until a filling material has been inserted in the same. The blocking in a working position of the metal insole is often difficult and not always successfully, due to the small space available for handling and holding the insole within the interstice for the time required for the insertion of the filling material.

In this context, the main technical task of the pre-sent invention is to suggest an accident prevention insole free from the drawbacks above mentioned.

In particular, an aim of the present invention is to provide an accident prevention insole capable of blocking pointed bodies independently from their perforation direction of the individual protection shoe sole.

A further aim of the present invention is to suggest an accident prevention insole, easy and fast to carry out, for an individual protection.

The stated technical task and the specified aims are substantially attained by an accident prevention insole including the technical features exposed in one or more of the appended claims.

Further features and advantages of the present invention will better result evident from the indicative, and therefore not limitative, description of a preferred but not exclusive embodiment of an accident prevention insole, as it is shown in the drawings, wherein:

FIG. 1 is a sectional perspective representation of an accident prevention insole according to the pre-sent invention set in a individual protection footwear;

FIG. 2 is a section along the plane II-II of the insole of FIG. 1;

FIG. 3 is another embodiment of the insole sectioned in FIG. 2; and

FIG. 4 is a further embodiment of the insole of FIG. 3.

With reference to the enclosed figures, by 1 an accident insole according to the present invention has been generally shown.

It has to be specified that by accident prevention insole is understood to mean, in the context of the pre-sent invention, an insole capable of withstanding, without being crossed through, to pointed objects. In particular, by accident prevention insole, an insole which is not crossed through by a nail with a diameter of 4.5 mm, or higher, which is driven perpendicularly to the insole with a force of 1100 N, has to be meant. The insole 1 includes a base surface 2 and a top surface 3 opposite to the base surface 2.

The insole 1 consists of a multilayer fabric 4 and can be crossed from the base surface 2 to the top surface 3 and vice versa, by needles with a diameter lower than 14 tenths of millimetre, driven perpendicularly to the insole 1 with a load of at least 90 N, for being directly sewn to an upper 101 of a footwear 100, preferably with a Strobel technique.

In particular, the insole 1 can be crossed from the base surface 2 to the top surface 3 and vice versa by needles with a diameter between 14 tenths of millimetres and 2 tenths of millimetre, preferably by needles with a diameter between 12 and 8 tenths of millimetres, still more preferably with a diameter of 11 tenths of millimetres, driven perpendicularly to the insole 1 with a load of at least 90 N.

Furthermore, the load with which the needles with the above mentioned dimensions cross-through the insole are between 90 N and 400 N, preferably between 100 N and 300 N, still more preferably between 150 and 250 N, in particular of 200 N.

In this way, advantageously, the insole 1 is able to intercept any nails which runs through, for example because it has been trampled, the insole 102 of the footwear 100 before the same can reach the foot sole of a user, independently from the angle with which the nails penetrates the sole.

Moreover, the fact the accident prevention insole can be directly sewn on the upper of a footwear allows to dramatically decrease the production costs of the individual protection footwears, as it not necessary to turn to complicated positionings of the insole within the sole.

As mentioned, the fact that the insole 1 subject of the present invention can be crossed-through by needles with dimensions lower than 14 tenths of mm, preferably with the dimensions above shown, allows to sew the same to the upper with a Strobel technique. For this purpose, it has to be noted that both the diameter and the force required for crossing-through the insole 1 are a function of the thickness of the insole 1. In any case, the insole 1 can be crossed by the needles commonly used and subjected to the usual forces exerted on the same by the sewing machines which carry out the Strobel technique, namely the common sewing machines which directly sew the insoles to the uppers of the shoes. This feature allows to further decrease the production costs of the individual protection footwears, as it is not necessary to turn to particular sewing techniques but it is sufficient to use sewing techniques and sewing machines (Strobel) well existing and deep-rooted in the footwear-sector.

Furthermore, the insole 1 can be advantageously cut and shaped directly by the shoe factory through the use of conventional templates, ensuring an optimization of the warehouse spaces. In fact, in this way, it is not necessary to arrange a warehouse including insoles already shaped according to a plurality of shapes and dimensions, but is possible to cut and shape insoles depending on the strictly required shapes and the dimensions.

Furthermore, the fact that the insole 1 consists of a multilayer fabric ensures a degree of shock absorption certainly greater than a metal insole, increasing the footwear comfort.

It has to be underlined that, from a protection point of view of the user's sole, the fact that the insole 1 can be crossed-through by needles with a diameter lower than 14 tenths of mm is practically insignificant. In fact, as usually the nails have a length which is substantially a function of the diameter, nails with a diameter lower than 14 tenths of mm can hardly reach the sole of a user, as their length is not sufficient to cross-through the thickness of the footwear sole.

In each case, nails having a diameter lower than 14 tenths of mm are not considered disabling, since they are not able to cause a significant damage to a user, as it happens, on the contrary, for nails with diameters of 4.5 mm or higher.

From a structural point of view, the insole 1, as mentioned, consists of a multilayer fabric 4. Each layer 5 of the multilayer fabric 4 includes a layer of fabric 6 and at least a resin surface layer 7. This latter is foreseen on each layer of fabric 6 and only covers the surface of the same, namely the resin surface layer 7 does not penetrate the fibers of the layer of fabric 6.

The resin surface layer 7 consists of a polyurethane and/or acrylic resin enriched with substances selected from the group including silicates, in particular iron silicate; alumina; silica; ceramic materials; glass-based materials.

Advantageously, such substances are associated with the resin in form of granules with a typical diameter between 1 tenth of mm and 1 mm.

As mentioned, the resin surface layer 7 does not penetrate deeply in the fabric layer 6 and has a thickness at least ten times lower than the thickness of the fabric layer 6.

Advantageously, the resin surface layer 7 imparts a greater compactness to the fabric layer 6, as it restrains together the yarns facing the surface of the fabric layer 6 wetted by the resin layer 7. Moreover, it has to be underlined that the resin surface layer 7, just because it does not deeply penetrate the fabric layer 6, ensures an optimal flexibility to the insole 1.

This latter feature, namely the flexibility of the insole 1, is very important, as it ensures a lasting service life of the same.

In fact, by subjecting the insole 1 to several bending cycles, it has been noted how the same, subjected to ten times the number of cycles which lead an accident prevention metal insole to a breakage, is still perfectly integral.

Advantageously, the resin surface layer 7 is not applied on the outer surface of the textile multilayer 4 intended for contacting the foot sole of the user.

This feature allows a better comfort of the insole 1, since, as it will result more apparent hereinafter, it is preferred to ensure an adequate humidity absorption and desorption rate to the insole 1 in correspondence with the zone intended for contacting the foot sole of the user.

As for the fabric layer 6, independently from the first or second kind of filaments used, it consists of an interlacement weave, namely a predetermined pattern of weft and warp yarns, the so-called double face. By double-face weave, it should be meant an interlacement weave through which the upper face of the fabric obtained is not symmetric, or it is not specular, with respect to the lower face of the same. A double-face weave, for example, is carried out by arranging two series of weft yarns through which, according to a predetermined pattern, a single series of warp yarns is passed.

Advantageously, the double-face weave allows to increase the weft density, that is the number of weft yarns per cm of fabric, of the fabric layer 6, by increasing the compactness of the fabric layer 6 itself. The high density of the weft ensures that a nail with large dimensions, namely with dimensions equal to or greater than 4.5 mm, is hold in one or more intersections of weft and warp until the weft and warp yarns break themselves or are displaced. The fact that the weft density is not infinite, as it occurs in the limit case of a metal foil, ensures that some needles with the specified dimensions can cross-through the insole 1 and therefore it can be sewn.

The double-face weave further allows to increase the covering degree of the end fabric, namely it allows to increase the ratio of the area effectively covered by the fabric to the nominal area of the same.

Furthermore, it has to be pointed out the contribution to the covering effect provided by the resin surface layer 7. In fact, as it is shown in the example 1 reported below, the covering is remarkably increased by the resin surface layer 7.

The covering of the multilayer fabric 4 is an important feature because it is directly bound to the ability of intercepting pointed bodies, such as nails. In fact, the higher is the covering effect, the higher is the probability of intercepting a nail which is pressed against the insole. The contribution given by the resin surface layer 7 to the covering effect is ensured by the grasp and holding effect that the granules, which enrich the resin, exert on the passage of the nail.

The fact that the covering of the multilayer fabric 4 is never total (see example 1) is at least partly responsible for the possibility of crossing the insole 1 with needles with a diameter equal to or lower than 14 tenths of mm, but arresting nails with a diameter greater or equal to 4.5 mm.

The weft and warp yarns of the fabric layer 6 consist of non aramidic fibers. This feature allows to remarkably decrease the production costs of the insole 1, since, as it is known, the aramidic fibers are definitely expensive and not always easily available on the market.

However, it has to be underlined that the insole 1 has accident prevention features, in the sense above specified, also apart from the use of aramidic fibers, as it will be better explained below.

In a first embodiment, shown in FIGS. 2 and 3, all the fabric layers 6 essentially consist of high-toughness polyester yarns, preferably of 1100 nominal dtex. More particularly, each yarn consists of a plurality of continuous twisted filaments, preferably 200, preferably with 60 twists per meter.

In a second embodiment, shown in FIG. 4, some layers of fabric 6 essentially consist of high-toughness polyester yarns with a nominal titer lower than that of the yarns of the first embodiment, preferably of nominal 238 dtex. More particularly, each yarn consists of a plurality of continuous twisted filaments, preferably 48, preferably with 120 twists per meter. In other words, in the second embodiment, the layers of fabric 6 are of two different typologies. In particular, the first typology foresees filaments with greater dimensions and greater toughness than the second typology.

Furthermore, in the first embodiment, namely the embodiment which foresees the use of filaments with greater dimensions and greater toughnesses than the filaments used in the second embodiment, a weave including 27 to 31 weft yarns per cm of fabric and 20 to 24 warp yarns per cm of fabric is foreseen.

In the second embodiment, the fabric layer 6 includes a weave having 90 to 92 warp yarns per cm of fabric and 32 to 36 weft yarns per cm of fabric.

Alternative embodiments foresee the use of yarns made of a material selected from the group including polypropylene, polyamide, polyamides, polyethylene, polyvyinyl, artificial filaments.

Advantageously, an outer layer of fabric 6, and particularly the fabric layer 6 a of the multilayer 4 intended for contacting the foot sole of a user includes filaments of cellulose material, preferably cotton, in order to absorb and release humidity. In this way, the accident prevention insole 1 ensures a high comfort since it allows the natural perspiration of the user's foot. Other cellulose materials utilizable are the linen, the hemp and the artificial celluloses.

In particular, the filaments of cellulose materials are introduced in the interlacement weave in an alternating way with respect to the above mentioned yarns, which form the interlacement weave. The alternation between yarns made of cellulose material and yarns forming the interlacement depends on the absorption and desorption degree that one wishes to reach. In the preferred embodiment, such alternation foresees a cellulose material yarn in weft every three yarns of weft.

It has to be noted how the cellulose material filaments do not substantially change the accident prevention features of the insole 1, as pointed out by the example 2 explained hereinafter.

Furthermore, apart from the presence of cellulose material, at least a layer of fabric 6 of the multilayer fabric 4 includes a plurality of monofilaments made of an electrically conductive material. Each of the monofilaments of an electrically conductive material is twisted on the outer surface of a weft or warp yarn. In other words, by foreseeing a filament of a conductive material on some weft or warp yarns, the insole 1 becomes electrically conductive and allows to dissipate electrostatic charges avoiding a potentially dangerous accumulation of the same.

Advantageously, in order to ensure a real effectiveness of the filaments of an electrically conductive material, this latter is introduced in a warp filament every 20-80 warp yarns, preferably every 23 warp yarns, and is introduced in two consecutive weft yarns every 20-80 weft yarns, preferably every 28 weft yarns. The fact of introducing two filaments of an electrically conductive material in two consecutive weft yarns allows to carry out an electrically conductive network in the insole 1. In fact, as mentioned, since the weave of each layer of fabric 6 is double-face, namely with a double layer of weft, the two filaments of electrically conductive material introduced in two consecutive yarns of weft ensure an electric contact between weft and warp, apart from the relative position within the fabric interlacement of the weft and warp yarns enriched with the electrically conductive material.

In the preferred embodiment, such filaments of an electrically conductive material consist of carbon monofilaments with a nominal titer of 24 dtex.

An example of the effectiveness of the filaments of electrically conductive materials is shown in the example 3.

Independently from the presence of cellulose material and electrically conductive material which, as pointed out, do not significantly alter the accident prevention properties of the insole 1, this latter obtains the mentioned accident prevention properties by foreseeing a textile multilayer 4 constituted by at least four layers 5, each including a textile layer 6 and a resin surface layer 7. Such configuration is shown in FIG. 2.

It has surprisingly been noted that it is possible to further reduce the textile fabric layers 6 without compromising the accident prevention properties of the insole 1 but, advantageously, reducing the weight and the production cost thereof. In fact, as shown in FIG. 3, the insole 1 can be carried out by a multilayer fabric 4 which includes three layers 5, in particular a first surface or end layer 5 a, a second end layer 5 b opposite to the first end layer 5 a and a central layer 5 c included between the first 5 a and the second 5 b end layers.

Advantageously, at least two 5 b, 5 c of the mentioned three layers 5 a, 5 b, 5 c include each a fabric layer 6 and two resin surface layers 7.

These two latter are arranged on opposite surfaces of the fabric layer 6.

As it can be seen by the example 4, the effect produced by the two resin surface layers 7 on the two layers of fabric 6 is to eliminate a layer 5 from the multilayer 4 without compromising the accident prevention properties of the insole 1.

Such effect is surprising since, as it can be seen in the example 4, the contribution to the accident prevention properties of the resin surface layer 7, individually considered, is almost negligible if compared with the one of the fabric layer 6.

However, it can be seen how the presence of the two additional resin surface layers 7 is substantially able to replace a fabric layer 6.

The above applies both for the first and the second embodiments.

It has to be underlined that the second embodiment above described further ensures the obtainment of an important advantage.

In fact, by foreseeing layers of fabric 6 including a thicker weave of 31 weft yarns and 24 warp yarns per cm of fabric and the use of thinner filaments, it is possible to arrest the penetration of a nail with dimensions even lower than 4.5 mm of diameter.

In particular, by foreseeing a multilayer 4 including at least five layers 5 of which at least three layers of fabric 6 as described with reference to the first embodiment and at least two layers of fabric 6 as described with reference to the second embodiment, the insole 1 obtained is able to arrest the penetration of nails with a diameter of 2, 5 mm, in addition to nails with a diameter of 4.5 mm, driven against the insole with a load between 300 N and 700 N, preferably between 400 N and 600 N, still more preferably of 550 N. More particularly, as reported in the example 5, by foreseeing two consecutive layers of fabric 6 constituted by filaments, preferably made of polyester, with a toughness of 238 nominal dtex and with a double-face interlacement weave thicker than the one with which the filaments with a toughness of 1100 nominal dtex are weaved, in combination with three consecutive layers of fabric 6 of the type with filaments at 1100 nominal dtex, nails with a diameter equal to or higher than 2.5 mm do not cross-through the insole when driven against the insole with a load between 300 N and 700 N, preferably between 400 N and 600 N, still more preferably of 550 N.

This effect is not obtained by using, for example, five layers of fabric 6 each having filaments of 1100 nominal dtex, in spite of the greater specific weight of such layers of fabric 6. In fact, it has to be underlined that, on average, a multilayer 1 consisting of five layers of fabric 6 each having filaments of 1100 nominal dtex has a specific weight of about 3300 grams per square meter, while a multilayer having two layers of fabric 6 each consisting of filaments of 238 nominal dtex and three layers of fabric 6 each having filaments of 1100 nominal dtex, has a specific weight of about 2900 grams per square meter.

A suitable method for carrying out the accident prevention insole 1 subject of the present invention foresees to interlace yarns of weft and warp of a non aramidic material according to a predetermined double-face weave, in order to obtain a single layer of fabric 6, spread the resin layer 7 on at least a surface of the single layer of fabric 6 obtained and firmly join together at least three layers of fabric 6 having the resin, layer 7 on at least a surface, for obtaining the multilayer 4.

Advantageously, before spreading the resin surface layer 7 on a fabric layer 6, this latter is subjected to a treatment in order to increase the hydrophilicity of the yarns of fabric 6 which will be involved by the resin layer 7.

In this way, the resin which forms the resin surface layer 7 better adheres to the fabric layer 6, ensuring that the filaments of weft and warp of the fabric 6 are strongly hold in their configuration.

Moreover, it has to be underlined that the treatment which makes hydrophilic the filaments of fabric 6 allows to effectively apply a greater quantitative of resin on the fabric 6 with respect to the same fabric 6 untreated.

In the preferred embodiment, the treatment which makes hydrophilic the filaments of fabric 6 is obtained through a plasma treatment of the surface of the fabric 6. In particular, by subjecting the surface of the fabric 6 which will receive the resin surface layer 7 with plasma discharges, the chemical bonds of the material forming the surface of the fabric 6 are modified, by increasing the receptivity degree of such surface to the resin of the resin surface layer 7.

The plasma treatment is preferably carried out in a nitrogen or carbon dioxide rarefied atmosphere.

Furthermore, advantageously, by treating the surface of the fabric 6 with a treatment for making the same hydrophilic before applying the resin surface layer 7, the effectiveness to the nails penetration increases, as it is shown in the example 6 reported below.

The step of spreading the resin surface layer 7 on a layer of fabric 6 is carried out, in the preferred embodiment, by applying 45-85 grams of resin at the fluid state every square meter of layer of fabric 6. Such spreading foresees to uniformly distribute the fluid resin on the fabric layer through the use of a knife which evenly distributes the resin. Preferably, the knife remains steady when the layer of fabric 6 is advanced below the same through conveyor rollers.

When the layer of fabric 6 has been uniformly coated with resin, the obtained layer 5 is passed in a dryer, for example a furnace, in order to dry the resin and makes it integral with the layer of fabric 6.

In case the layer of fabric 6 is previously treated in order to render hydrophilic the surface of the same, the deposition of the resin layer 7 must be carried out within seventy-two hours from said treatment.

In fact, it has been noted that when this time has elapsed, the surface of the fabric layer 6 looses its hydrophilic properties.

In case the fabric layer has to be coated in both the surfaces with a resin surface layer 7, the layer of fabric 6 already having a dried resin surface layer 7 is easily turned upside-down and on the obtained layer 5 the spreading and drying operations above mentioned are repeated.

The step of firmly joining together the layers 5 obtained consists of the application, between a layer 5 and the following sheet, with a thickness of few tenths of microns, of a thermoplastic material. The layers 5 with interposed thermoplastic material sheets, are passed through a heated cylinder opposite to a high-temperature-resistant felt carpet, which provide to melt the thermoplastic material sheets and join together the different layers 5 of the textile multilayer 4.

It has to be underlined that the contribution of the thermoplastic sheet to the accident prevention properties of the insole 1 is almost insignificant, having as a unique effect the one of rendering integral together the layers 5 which constitute the multilayer fabric 4.

EXAMPLE 1

Sample 1: a sample consisting of a fabric layer according to a fabric layer 6 above described has been arranged. In particular, the fabric layer is made of continuous multifilament polyester yarns with a high toughness of nominal 1100 dtex.

The polyester yarns have been interlaced with a weft density of 29±2 yarns per cm and a warp density of 22±2 yarns per cm. The interlacement weave is a double-face weave. The specific weight of the fabric is 590 gr/sq.m.

Sample B: a sample identical to the sample A has been arranged, with the addition of a resin surface layer according to what described. In particular, the resin layer consists of 54% acrylic, 44% polyurethane and 2% iron silicates. Such resin layer has been applied in a quantity of 70 gr/sq.m. on the fabric of the sample A and dried.

Sample C: a multilayer fabric, consisting of five superimposed layers, has been arranged, four consecutive layers are each identical to the layer of the sample B and the last layer is the same to the layer of the sample A.

Amongst two opposite surfaces of each sample, a pressure difference of 200 Pa for 60 seconds has been applied and the air volumetric rate per surface unit flowing through the sample has been measured. The results are reported hereinafter (the means are arithmetic means).

Sample A Sample B Sample C Number of tests 5 6 2 Mean air rate 46.0 2.9 0.5 [mm/sec.]

EXAMPLE 2

Sample D: a multilayer fabric consisting of four superimposed layers has been arranged, three consecutive layers are each identical to the layer of the sample B of the example 1 and the last layer is identical to the layer of the sample A of the example 1.

Sample E: a multilayer fabric consisting of four superimposed layers has been arranged. The layers are identical to those of the sample D, except for the fact that one of the two outermost layers includes 1 cotton yarn in weft every three polyester yarns in weft.

The samples are subjected to a cycle including the bending of the sample and the inflow of 7.5 ml/min.±2.5 ml/min. of water on the sample surface. The samples are further subjected to a load of 80 N±5 N during the bending. Such cycle is repeated for 4 hours and at the end the water quantity retained by the sample, expressed in mg of water retained per cm² of sample, is measured.

Subsequently, the sample is placed in a temperature and humidity-controlled environment for 24 hours and the water quantitative released by the sample with respect to the absorbed water is measured. The results are reported below.

Water absorption Water desorption [mg/cm²] [%] Sample D 50 95 Sample E 88 94

A nail with a diameter of 4.5 mm has been advanced at a rate of 10±3 mm/min. perpendicularly to the samples. The force required for perforating the samples has been measured. The results are reported below.

Test 1 Test 2 Test 3 Force [N] [Force] N Force [N] Sample D 1610 1580 1580 Sample E 1340 1280 1240

The samples have been subjected to two kinds of thermal aging and the perforation test has been repeated. The first kind of thermal aging foresees to subject the samples at a temperature of 333 K for 4 hours. The second kind of thermal aging foresees to subject the samples at 253 K for 4 hours. The results are reported below.

Kind of Test 1 Test 2 Test 3 thermal aging [Force] N [Force] N Force [N] 1° Sample D 1680 1660 1670 1° Sample E 1320 1290 1280 2° Sample D 1900 1860 1870 2° Sample E 1310 1260 1240

The samples have been subjected to two kinds of chemical aging and the perforation test has been repeated. The first kind of chemical aging foresees to subject the samples to a dipping in a sulphuric acid solution at a temperature of 293 K for 24 hours. The second kind of chemical aging foresees to subject the samples to a dipping in a sodium hydroxide solution at a temperature of 293 K for 24 hours. The results are reported below.

Kind of Test 1 Test 2 Test 3 chemical aging [Force] N [Force] N Force [N] 1° Sample D 1540 1560 1550 1° Sample E 1210 1200 1200 2° Sample D 1510 1500 1500 2° Sample E 1220 1225 1200

EXAMPLE 3

Sample F: a sample identical to the sample E of the example 2 has been arranged.

Sample G: a sample identical to the sample F with the addition of a carbon monofilament, with a nominal titer of 24 dtex, on a warp yarn every 23 warp yarns and a carbon monofilament, with a nominal titer of 24 dtex, on two consecutive weft yarn every 28 weft yarns.

A potential difference of 250 V has therefore been applied to the ends of each sample and the resistance of the two samples after a minute of electricity passage has been measured. The results are the following:

Resistance [MOhm] Sample F Between 5000 and 10000 Sample G Between 1000 and 3000

EXAMPLE 4

Sample H: a sample identical to the sample A of the example 1 has been arranged.

Sample I: a sample identical to the sample B of the example 1 has been arranged.

Sample L: a sample identical to the sample I has been arranged, with the addition of a further resin surface layer on the opposite side with respect to the resin layer already applied. The further resin layer has identical features to the one already applied.

Sample M: a multilayer consisting of three superimposed layers has been arranged. In particular, two consecutive layers consist, each, of an identical layer to the one of the sample L and the remaining layer is identical to the layer of the sample I.

A nail with a diameter of 4.5 mm has been advanced at a rate of 10±3 mm/min. perpendicularly to the samples. The force required for perforating the samples has been measured. The results are reported below.

Test 1 Test 2 Test 3 Force [N] [Force] N Force [N] Sample H 270 275 290 Sample I 300 320 300 Sample L 340 320 360 Sample M 1205 1190 1180

EXAMPLE 5

Sample N: a sample like the sample C has been arranged. In other words, it is a sample consisting of 5 layers.

Sample O: a sample like the one of the sample N, in which the two consecutive layers of fabric have been replaced by two layers of fabric, each one carried out with continuous multifilament polyester yarns, with a high toughness of nominal 238 dtex, has been arranged. The polyester yarns have been twisted with a weft density of 34±2 yarns per cm and a warp density of 92±2 yarns per cm. The interlacement weave is a double-face weave. The specific weight of the fabric is 430 gr./sq.m.

A nail with a diameter of 4.5 mm has been advanced at a rate of 10±3 mm/min. perpendicularly to the samples. The force required for perforating the samples has been measured.

A nail with a diameter of 2.5 mm has been advanced at a rate of 10±3 mm/min. perpendicularly to the samples. The force required for perforating the samples has been measured.

The results are reported below.

Test 1 Test 2 Test 3 Force [N] [Force] N Force [N] Nail 4.5 mm Sample N 1680 1730 1750 Sample O 1260 1300 1280 Nail 2.5 mm Sample N 590 560 590 Sample O 630 700 680

EXAMPLE 6

Sample P: a sample identical to the sample M has been arranged.

Sample Q: a sample identical to the sample O has been arranged.

Both the samples have been subjected to a preventive hydrophilic treatment before the deposition of the resin surface layers.

A nail with a diameter of 4.5 mm has been advanced at a rate of 10±3 mm/min. perpendicularly to the samples. The force required for perforating the samples has been measured. The results are reported below.

Test 1 Test 2 Test 3 Force [N] [Force] N Force [N] Sample P 1325 1310 1300 Sample Q 1390 1430 1410 

1-12. (canceled)
 13. Accident prevention insole including a base surface and a top surface opposite to the base surface, wherein: said insole consists of a multilayer fabric; said insole can be crossed-through from the base surface to the top surface and vice versa by needles with a diameter lower than 14 tenths of millimetres, preferably between 14 and 2 tenths of millimetres, driven perpendicularly to the insole with a load of at least 90 N, preferably between 90 N and 400 N, for directly sewing the insole to an upper of a footwear, preferably with a Strobel technique.
 14. Insole according to claim 13, wherein each layer of said multilayer fabric includes a fabric layer and at least a resin surface layer applied to each fabric layer in order to increase the covering; each fabric layer consisting of non aramidic fibers.
 15. Insole according to claim 13, wherein the interlacement weave of each fabric layer is a double-face weave for increasing the weft density.
 16. Insole according to claim 13, wherein at least a fabric layer, preferably faced to the top surface, includes cellulose material filaments, preferably cotton, in order to absorb and release humidity.
 17. Insole according to claim 13, wherein at least a fabric layer (6) includes a plurality of monofilaments made of an electrically conductive material; each of said monofilaments of electrically conductive material being twisted on the outer surface of a weft or warp yarn.
 18. Insole according to claim 13, wherein to at least a fabric layer two resin surface layers are applied; said two resin surface layers being arranged on opposite surfaces of said fabric layer.
 19. Insole according to claim 18, including two outer layers of fabric and one central layer of fabric interposed between the two outer layers, wherein both the central layer and one of the two outer layers include each two resin surface layers.
 20. Insole according to claim 13, including five layers of fabric; two of said five layers consisting of filaments with a toughness and a diameter lower than the filaments of the other three layers of fabric; said two layers having an interlacement weave thicker than the one of the other three layers for resisting to the perforation of nails with a diameter higher than 2.5 mm driven perpendicularly to the upper with a load lower than 600 N, preferably between 400 N and 600N.
 21. Insole according to claim 13, wherein the fibers of each layer of fabric are yarns made of a material selected from the group including twisted continuous multifilament polyester, polyamide, polyamides, polypropylene and artificial filaments.
 22. Method for producing an insole according to claim 13, including the steps of: twisting yarns made of a material selected from the group including polyester, polyamide, polyamides, polypropylene and artificial filaments, according to a predetermined double-face weave, in order to obtain a fabric layer; increasing hydrophilicity of at least a surface of said fabric layer, preferably through a plasma treatment of said surface; spreading a resin surface layer on said at least one surface of the obtained fabric layer; firmly joining together at least three layers of fabric having the resin surface layer on at least a surface in order to obtain a multilayer fabric.
 23. Footwear including an upper and an accident prevention insole according to claim
 13. 24. Footwear according to claim 23, wherein the accident prevention insole is sewn to the upper. 